Aluminum alloy



' proved alloy of aluminum, zinc and mag ncsium, which is of particular utihty for the Patented Mar. 30, 1926.

human stares TRUMAN S. FULLER AND DAVID BASCH, OF SCHENECTADY, NEW YORK, ASSI GNORS' Parana" oFFicE.

TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

- ALUMINUM annoy.

No Drawing. Continuation of application filed December 13, 1923, Serial No. 680,516. This application filed December 18,1924. Serial in. 756,822.

The present invention is a continuation of our application, filed December 13, 1923, Serial No.- 680,516, and comprlses an immanufacture of castings.

Alloys comprising these ingredients have been known heretofore in which a content of magnesium of a few per cent has been accompanied by a zinc content of approximately 20% or conversely in which a magnesium content of as high as 10% has been accompanied by the low zinc content of about 1%; also alloys are knowncontaining a fourthingredient, such as iron, in addition to the three ingredients mentioned.

lVe havediscovered that an alloy of exceptionally good physical properties results from the combination of aluminum, zinc and magnesium in the proportions of about 3 to 8 parts zinc and about 0.25 to 1.5 parts magnesium, the balance of the alloy being aluminum except, of course, for incidental impurities. In our'above prior application, Serial No.- 680,516, we have described a cast alloy comprising about 92.7 5 parts aluminum, about 6 parts zinc and about 1.25 parts magnesium -which has'a tensile strength of about 26,000-

peunds per square inch and a hardness of about 7 5 Brinnell. The elastic limit (proportional limit) of this alloy is about 12,000 pounds per square inch. Although for some purposes this alloy is entirely suitable without further treatment, its properties may be improved by heat treating. For example, the alloy is heated to about/ 515 C. for. about twenty-four hours, then-is quenched in boiling water and finally is aged either artificially at about 150 C. for three hours or more, or naturally. By this treatment the tensile strength is increased to about 35,000 pounds per square inch and the hardness is raised to about 104 Brinnell.

A. cast alloy containing 0.5 parts magnesium and 5 parts zinc. the balance being aluminum (exceptfor impurities) has an ultimate tensile strength of about 2 1,000 pounds per square inch. The'elastic limit of the alloy is about 7,000 to 8,000 pounds per square inch. The elongation of the alloy as measured by the tensile strength tests is about 4 to 8 per cent.

In general in an alloy constituting our invention, the proportion ofzinc preferably is maintained Within the limits of about 4 to 6 per cent, and theproportion of magnesium preferably is maintained within the limits of about 0.5 o 1.25 per cent. As al.-

ready indicated, good results are obtained I even when the zinc content is as low as three or as high "as eight per cent or when the magnesium content is as low as 0.25 or as high as 1.5 per cent.

An aluminum alloy having a composition within theselimits flows freely in a mold,

forms castings having sharp outlines. and

may be readily Worked by machine tools.

It may be used either without heat treat ment in'the state obtained by casting or when improved by heat treatment.

/Vhat we claim as new and desire to secure by Letters Patent of the United States, is:

1. An alloy consisting essentially of aluminum, zinc and magnesium, the zinc content of said alloy beingwithin the limits of about three to eight per cent and the mag nesium. content being within the limits of,

about-0.25 to 1.5 per cent.

2. An alloy suitablefor casting essentially consisting of about 0.5 to 1.25 per cent of magnesium, about 4 to. 6 per cent of zinc, the balance of the alloy being aluminum except for incidental impurities.

, In witness whereof, We have hereunto set our hands this 17th day of December, 1924.

' TRUMAN 'S. FULLER;

DAVID BASCH. 

